Alkylation of isoparaffins by means of normal olefins in the presence of hydrofluoric acid



Aug..26, 1947. M. P. MA'ruszAK 2,426,559

OP'ARAFFINS BY MEANS OF NORMAL OLEFINS RESENCE OF HYDROFLUORIC ACID ALKYLATION oF 1s IN THE P Filed Aug. 21, 1944 Patented Aug. 26, 1947 ALKYLATION F ISOPARAFFINS BY MEANS OF NORMAL OLEFINS IN THE PRESENCE 0F HYDROFLUORIC ACID Maryan l?. Matuszak, Bartlesville, Okla., assigner to Phillips Petroleum Company, a corporation of Delaware Application August 2l, 1944, Serial No. 550,447

2 Claims.

This invention relates-to the conversion of hydrocarbons in the presence of hydrouorie acid. In a particular embodiment of this application it relates to the alkylation of low-boiling isoparaiiin hydrocarbons by reaction with low-boiling normal olefins such as propylene, butene-l, butene-2, pentene-l, pentene-2, and the like. Particular advantages result from the specic embodiment wherein isobutane is alkylated by reaction with butene-l.

At present, one important commercial method of converting low-boiling hydrocarbons into motor-fuel hydrocarbons is alkylation of isoparafiins with olelins in the presence of catalysts such as hydrouoric acid and sulfuric acid. In present commercial processes using hydroluoric acid the hydroluoric acid is preferably anhydrous, and the presence of water is generally considered, on the basis of results obtained in the hydrofluoric acid alkylation of isobutane vn'th isobutylene, to be highlyundesirable because it increases corrosion ci equipment, decreases alkylate yield and quality, and increases formation of organic fluorine compounds, which must be removed from the allrylate at considerable trouble and expense.

Contrary to the teachings of the prior art, I have made the surprising and unexpected discovery that, vin the hydroiiuoric acid alkylation of iso'butane. with anormal butylene, especially butene-l, the presence of a minor amount of water in the hydrofluoric acid leads to the production of an alkylate so superior-in octane rating that the disadvantages attendant upon the presence of Water are much more than counterbalanced. It may be emphasized at the outset that the advantages of the present invention attendant upon the presence of water in the hydrofluoric acid are obtainedonly when the olen isa normal olefin and are obtained in the highest degree when the olefin is butene-l; they are not obtained when the olen is an isoolefin, such as isobutylene'.

Among the objects of this invention is to provide Yan improved process for the conversion of hydrocarbons.v

Another object is to provide an improved 'process for alkyla-ting isobutanewith a normal butylene; whereby the alkylate obtained has an octane rating'vhigher than that of the alkylate obtained under comparable conditions by conventional hydrofluoric acid alkylation. n

A further object of my invention is to alkylate low-boiling isoparains.

Another o'bject is to provide a process for utilizing hydrofluoric acid containing a limited proportion of water as a relatively superior catalyst for the alkylation of isobutane with butene- 1.

Other objects and advantages will be apparent from the accompanying description and disclosure.

This invention has resulted from a continuation oi the experimental and inventive activity evidenced by my copending applications, Serial Number 467,872, now- Patent 2,399,368, issued April-30, 1946,V SerialfNumber 467,873, and Serial Number 467,874, now Patent 2,387,162, issued October 16, 1945, all of which were led December 4, 1942, and-of which this application is considered to be a continuation-impart'insofar as any common subject matter is concerned. The lastmentioned copending application is a continuation-in-part of my application Serial Number 395,282, filed May 26, 1941, now Patent 2,320,629, issued June 1, 1943.

As was pointed out in these copending applications, in present-day acid-catalyzed alkylation processes for reacting parafns with olens to l produce heavier paraflins, the principal or major constituents of the alkylate produced are those which would be formed if one olen molecule added to one paralin molecule by a mechanism termed parailin-oleln juncture. In such juncture, apparently a hydrogen or a methyl group from the original paraffin becomes attached to one of the two double-bond carbon atoms of the original olen, and the rest of the original paraiiiii becomes attached to the other double-bond carbon atom. The number of carbon atoms per molecule of the major components of the product is accordingly equal-to thesu-m of the numbers of carbon atoms per molecule ofthe paran and the oleiin reactants. Only a limited number of the many possible paraln isomers characterized by this number of carbon atoms per molecule are formed as-primaryvproducts of simple paraffinolen junctures.- However, other isomers may be formed by secondary and side reactions, such as isomerization of the primary alkylate, isomerization of the original oleiin prior to the alkylation reaction, dimerization of the original ol'en accompanied or followed by hydrogenation of the dimer, and the like.

Heretofore, those skilled in the artof alkylation have directed their efforts mainly towards increasing the extent of the simple paraiin-olen juncture and towards decreasing the extent of side reactions, especially polymerization of the olefin. However, in many instances, speciiic side reactions other than polymerization produce constituents in the Yalkylate that are more desirable and valuable than those producedby'the juncture of the initial parain with the initial olefin. Such a desirable side reaction is believed to be promoted in the'process of the present invention, whereby apparently a relatively increased proportion of one or more relatively high-octanenumber octanes, particularly2,2,4-trimethyl pentane, is produced inthe alkylate.

This particular octane is the primary alkylate formed by parafIin-olefin juncture inV the hydrofluoric acid alkylation of isobutanc with isobutylene. Although it is also formed to a small extent in the hydrofluoric acid alkylation of isobutane with a normal butylene, no fully satisfactory explanation of its formation from these particular reactants has been available, and no economical and readily practicable means for promoting or increasing its formation has thus far been proposed.

The following theoretical explanation or mechanism for the formation of 22A-trimethylpentane in the acid-catalyzed alkylation of an isoparafn with an olefin is offered solely for the purpose of aiding an understanding of some aspects of the present invention.

In the presence of an alkylation catalyst such as hydrouoric acid, the isoparaiiln appears to ionize in at least two ways, each yielding a positive ion and a negative ion, which for convenience may be designated and differentiated from each other by adding to the root form of the corresponding radical the terminations ium and ide, respectively. For example, isobutane ionizes to either hydrium (proton or positive hydrogen ion) and isobutide or methium and isopropide, as follows:

I (I3-I H AWHI- I I I -rrfe Isobutane Hydrium Isobutide I I (IJ-I I -C-C-C* -C -I- O O- l l l I l I l Isobutane Methium Isopropide forming ionization. For isopentane, the me-V thium-forming ionization appears to predominate over the hydrium-forming ionization to an extraordinarily high degree:

Y yI I I --0- (T2 H -I- C-C-C- I I I I I I Isopentane Hydrium Isopentide (orisoamide) ThisY predominance of methium-forming ionization in the case of isopentane is of exceedingly great significance because it indicates an group has a strong tendency to lose the methyl group in this ethyl group by liberation of methiurn. This tendency naturally increases withthe size and the complexity of the hydrocarbon molecule, with the possible exception of hydrocarbons having the structure of 2,3-dimethylpentane, such as 2,3,3-trimethylpentane, in which it is apparently internally counterbalanced to some extent. It is almost undetectable in propane, but it increases in normal butane to the eXtent that advantageous isomerization to isobutane can occur by an over-all succession of methium-forming ionization, hydrogen shifting (which may involve hydrium-forming ionization), and recombination of ions:

I I C-O-C- l l I l I Normal butane Methium n-Pz'opde I I I I I lC-C-C- d -C-O-C- I I I I I I n-Propide Isopropide I O I I I I I I arr-+r? e ff-rfi- Methium Isobutane Isopropide This strong tendency for an ethyl group to undergo methium-forming ionization appears to account for the fact that the alkylation of isopentane can give the high yields of concomitantly formed isobutane and isoheXane that are indicated in my aforementioned copending application, Serial Number 467,872; for the isobutide for the methium-forming ionization of one isopentane molecule can unite with the hydrium `from the hydrium-forming ionization of another isopentane molecule to yield a molecule of isobutane, and, similarly, the methium and the isopentide can unite to form a molecule of isohexane. In similar fashion, in the alkylation of isobutane, the formation of propane and of isopentane can be accounted for by the combination of hydrium with isopropide and of methium with isobutide, respectively; however, it vdoes not necessarily follow that such propane and such isopentane are formed in molecularly equivalent amounts, for the hydrium and the isopropide corresponding to the methium and the isobutide that unite to form isopentane may be selectively consumed in other reactions.

The ionization of parans in hydrofluoric acid and recombination of ions to form either the f original or new paraflins is apparently promoted by the presence of an olen. The reason for the promotionA appears to be that the olefin has a strong tendency to acquire a positive ion, such as hydrium, by the following mechanism, exemplifled for butene-l, which forms principally secondary butium:

Hydrium I Butene-l dipole Sec-butiuni Butene-l Butene-l dipole `B`utenel dipole Primary butium In similar fashion, but'ene-'Z yields substantially only secondary rInutium:

vBy this mechanism methium may be added similarly, instead o'f hydrium, but the resulting .positive ion differs for butene-l and butene-2:

VThe resulting positive ion logically can combine with any of the negative hydrocarbon ions present to form a primary-alkylate paraflin (for simplicity the carbon-hydrogen bonds in the product may be omitted) The'identity and the relative proportion of any particular primary-alkylate paraffin produced in this 'matter depends on'th'e'id'entityand'the relativeproportions of the ionsthat unite to form the paraffin.

Certain of the theoretical primary-alkylate products contain, just as does isopentane, one or more ethyl groups. In consequence, these products have a relatively high tendency to 'undergo methium-forrning ionization, and the resulting negative ion then may undergo reactions like those. already exemplified. For example, 2,4-dimethylhexane, Which is theoretically a major primary product in the alkylation of v-isobutane With a normal Ibutylene, may undergo Lan isomerization similar in mechanism to that already shown for the isomerization of normal butane (but far more facile because of the relatively larger size and complexity of the molecule) C C-C-C-C C--G t C C-QI-C C-(Il-C 2,4-dimethylhexane 2,2,4-trimethylpentane Ii, instead of undergoing a hydrogen shift and then recombining with' methium, the negative ion preliminarily formed by methium-forming ionization acquireshydrium, 2,4-dimethylpentane is formed. Similarly, vfrom 2-methyl-4-ethylhexane may be'formed 2,4,4-trimethylhexane or 2,4-dimethylhexane, depending on whether the negative ion formed by the methium-forming ionization eventually combines with methium orwith hydrium; inasmuch' as each of these products still contains an ethyl group, further reaction may occur, to form such final product paraiins as 2,2,4-trimethylpentane and 2,4-dimethylpentane. Similarly, other primary-alkylate parains containing ethyl groups are converted, at least in part, to other paraiins that do not contain ethyl groups. In consequence, such a paraffin as 2- rnethyl-S-ethylpentane, which is formed only in relatively small proportion and which contains at least one ethyl group, is practically absent from the final alkylate, whereas such a paraiiin as 2,3,4-trimethylpentane, which also is formed in relatively small proportion but which does not contain as ethyl group, survives and can be isolated from the nal alkylate.

The foregoing simple but far-reaching theoretical explanation or mechanism of acid-catalyzed alkylation presents a clear, logical picture of the reactions that take place. It appears to account remarkably Well for most if not all of the experimental facts known at present in the field of acid-catalyzed alkylation. For present purposes, it need not be made exhaustive, so that no attempt need be made herein to account explicitly for the presence or the absence of each and every alkylate product.

In this mechanism, a limited proportion of Water can play a role that is apparently similar to the initial role of the olen, that of promoting the ionization of various Vparailins by acting as a hydrium or methium acceptor. Understanding ,of this theoretical conception may be facilitated by a consideration of the nature of hydrofluoric acid, particularly strong or substantially anhydrous hydroiiuoric acid as distinguished from a dilute aqueous solution. The nature of this material is most simply comprehended by a realization tlri'at it is the fourth member of the series: methane, ammonia, water, hydroiluoric acid.

Electronically, these compounds may be represented as follows:

l lilo* 40; l F

In this series, each member has one more lone electron pair than the preceding member. Each member has a tendency to acquire thestructure present in methane, that is, to have four hydrogen atoms each bound to the central atom by an electron pair. This tendency is obviously strongest in ammonia, which unites or coordinates with hydrium to form the positive ammonium ion present in ammonium salts:

ofwi H a le This tendency is relatively less strong in water, which however, does form the positive hydronium (hydroxonium) ion:

Understandably, this tendency is least strong in hydrofluoric acid, which in fact attracts fluoride rather than hydrium, forming a complex negative ion containing a, hydrogen bridge:

Although this last equation appears to indicate a difference in kind rather than a difference in degree between h'ydrofluoric acid on the one hand and ammonia and water on the other, the fact is that the difference is only one of degree, as may be readily realized from the consideration that hydroiiuoric acid polymerizes and that both ammonia and water combine with hydrouoric acid to form salts. Of these salts, the salt from ammonia, ammonium fluoride, is quite stable and is well known in solid form, whereas the corresponding salt from water, hydrom'um (or hydroxonium) fluoride, is relatively less stable, so that it is known chiefly in solution, although it undoubtedly can be isolated as a solid at low temperatures; corresponding to these two salts is the relatively still less stable dimer of hydrouoric acid. The gradation among these three substanances is readily seen from the following electronic equations for their formation:

Ammonia Hydrciuoric acid Ammonium fluoride Hydronium fluoride zation of paraflins `by theacceptance or acquisition of hydrium or methium to form the corresponding positive oxonium ion. However, the proportion of water present must be limited, for too large a proportion changes the system from one in which hydrouoric acid is the solvent to one in which water is the solvent, and the nature of the reactions that can take place is correspondingly greatly changed. Apparently, when the Iproportion of water is gradually increased, the solubility of the parainn is correspondingly decreased, wherefore the ionization of the parafin is likewise decreased, and the alkylation reactions are correspondingly hindered. Concurrently, ionization of hydrofluoric acid into hydrogen and iluoride ions is correspondingly increased, so that any positive ion formed by the union of an oleiin molecule and a hydrogen ion is caused to unite with a fluoride ion rather than with a negative hydrocarbon ion of the type of isobutide, isopropide, or the like. In consequence, the olen is largely consumed in the formation of the corresponding alkyl fluoride instead of undergoing juncture with a parafln.

In accordance with one aspect of this invention, the formation of molecules of hydrocarbons having high octane numbers is promoted by the presence of a minor, or limited, proportion of water in the hydroiiuoric acid. From the results of extensive experimentation, it has been found that the proportion of water in the hydrofiuoric acid should be between approximately 2 and approximately 10 per cent by weight of the hydrogen fluoride, exclusive of any dissolved organic material, when normal butenes are the alkylating olefins. The optimum proportion for any particular set of selected alkylation conditions may be readily determined by trial; usually the optimum proportion in alkylating isobutane with butene-l is between 4.0 and 6.0` per cent by Weight, so that the proportion is preferably adjusted to approximately 5.0 percent. This proportion is rather critical from the point of view of obtaining an alkylate of the highestpossible octane rating. If too little water is present, the alkylation degenerates into the conventional alkylation; if too much is present, the olen is consumed in formation of the corresponding alkyl fluoride, accompanied by considerable polymerization, and the resulting product is inferior in both yield and octane rating and contains an excessive proportion loi" organic fluorine compounds. However, the critical limits of the proportion Yof -water in hydroiiuoric acid alkylation with butene2 appear to differ somewhat from those found for butene-l, under otherwise substantially identical alkylation conditions. That is, in alkylation of isobutane with butene2, the optimum proportion of water appears to be between approximately 2.0.and approximately 4.0 per cent by weight of the hydrogen fluoride in the catalyst, so that the proportion is preferably maintained at approximately 3.0 per cent. For alkylating an isoparain with a mixture of normal butylenes, n the preferred proportion of water may be calculated in accordance with the proportions of these butylenes in the olen feed; for example, for an olen feed containing approximately equal proportions of butene-l and of butene2, Ythe preferred proportion of water is approximately 4.0 per cent by weight of the hydrogen uoride in the catalyst. In alkylating with solely isobutylene, however, no Water preferably should be present in the catalyst; hence, when the alkylation is being made with a rnX- ture containing (one ror .both normal butylenes Y throughconduit 'I to and isobutylene, the proportion of Water should be adjusted in accordance with the proportions of the specific butylenes present. For example, for alkylating With a mixture containing approximately equal proportions of butene-l, butene-2, and isobutylene, the proportion of Water should preferably be adjusted to approximately 3.0 per cent by Weight of the hydrogen fluoride. It will be understood that adjusting the proportion of Water in this manner is in the interest of obtaining the optimum octane rating for the over-all alkylate produced.

A detailed explanation of one embodiment of this: invention may be made with reference to the accompanying drawing, Whichis ra schematic flowdiagram exemplifying a preferred manner of converting four-carbon parains to motor-fuel paraiiins.

A mixture of isobutane and normal butane entering; theQsystem through inlet I is separated into its components by fractionator- 2. The isobutane is passed through conduits 3 and v4 to alkylators 5- and 6, which preferably areY so designed that the incoming isobutane sweeps any corrosivemixture away from any bearingV box or packing gland. The-normal butane is passed dehydrogenator 8, in which it is Ycatalytically dehydrogenated in known/Inanner-to normal butylenes. The resulting dehydrogenation eilluent is passed throughconduit 9 to fractionator I0, Which comprisesV a system of fractional-distillation columns. From this system, butene-l is passedv through conduit II. to the isobutane stream in conduit 3 undehydrogenated normal butane is recycled through conduit I 2to-dehydrogenator 8; butene-Z is passed throughfconduit I3 -to the isobutane stream in conduit4;' and ley-products of the dehydrogenation are removed, mostly as a low-boiling fraction, in a'manner'obvious to those skilled in the artas through conduit IDA;

Ineachof alkylators5 andILthe incoming mixture'i ofisobutane and normal' butylene is intimately'mixedunder alkylation conditionsvvith an alkylation catalyst, which enters the alkylator from conduit LI4"or I5,'respectively. For alkylator 5; in Which thealkylating butylene is-butene-l, the catalyst isy hydrofluoric acid vcontaining approximately 5.0 per cent' by weight of water; for alkylator 6,' in` Whichthe alkylating'butylene is butene-2, the catalyst is hydrouoric acid containing about 3.0 per cent by Weight of Water. Except for the difference in Water content of the hydrouoric acid, the alkylation conditions in the twoz'alkylators `may bei substantially alike. Tli'epressurev should be'sufli'cien't to'maintain the reaction mixture in liquid phase, but above this point it may be as: high as may be desired for such purposes as effecting proper movement of the various streams in the system or the like. The temperature andthe contact time, or average time; of'residence' or mixing inV the alkylator,y may varywidely;v fora'temperaturein the range of 90 to 1'20"F'.',. which is, preferred as beingk readily obtainableA Iby 'Water-cooling; the contact time is preferably. approximately 10 minutes. The volume ratio of' hydrocarbons to hydrofluoric acid in the alkylator ispreferablyY approximately 1:1. The mol'fratiov of isobutane to butylene in the incoming hydrocarbon stream is preferably as high as is economically feasible; usually it is from 4'1-1 to v210:1.

` The reaction mixture eilluent from alkylator 5 ispass'ed'fthrough` conduit I6 to separator I1, in

which itis separated-by. gravity into. two liquid 10 phases. The hydrocarbon phase may be passed through conduits I8 and 34 to fractionator I9 for separation into various fractions, but it is preferably passed through conduit 29 fto extractor 2 I` for removal of organic fluorine compounds by extraction With substantially anhydrous hydroiiuoric acid, which is introduced through conduit 22, ina manner indicated in the aforementioned Patent 2,320,629. The hydrofluoric acid phase from separator Il in part is recycled through conduit I4 :to alkylator 5 and in part is passed through conduit 24 to fractionatorV 25. From fractionator 25, anhydrous hydroiiuoric acid, accompanied by some light hydrocarbons, is passed overhead through conduit 422 tol extractor 2I; a constantboilingaqueous hydrofluoric acid, containing approximately 40 per cent of hydrogen fluoride, is

`passed in, part through conduit 26 to alkylator 5 and in part through conduit 21 to alkylator 6, but part or all of it may be Withdrawn, if desired, through outlet 28; and a relatively small fraction of so-called acid-soluble oil is Withdrawn through outlet 29. Make-up hydrofluoric acid, which is obtained commercially in'substantially anhydrous form, may be added as required throughinlet 30,Y and make-up Wateris added as required through inlet 3I.

The reaction mixture effluent from alkylator 6 is passed through conduit 32 toseparator 33, in which Vit is separated by gravity into two liquid phases. The hydrocarbonV phase may be passed through conduit 34 to fractionat'or IB'for separation into various fractions, Vbut it YisV preferably passed through conduit 35 'to' extractor 2I for removal of-organic fluorine compounds by extraction With hydrofluo-ric acid; inasmuch as this hydrocarbon phase at times contains slightly less organic luorine than `the hydrocarbon phase from separator I'I, it is preferably introduced into extractor 2| at a point correspondingly relatively upstream with respect to the stream of extracting acid. The hydrofluoric acid phase from separator 33 in part is recycled throughconduit I5 to alkylator Ii and in part is withdrawn' through outlet 3l or, preferably, is passed through conduit 38` to fractionator 25 for purification. Makeup hydrofluoric acid may be added through inlet 39, but it is preferably added entirely through inlet 4D to extractor ZI make-up water, when required, may be added through inlet 4I, but ordinarily sufficient Water is brought in in the acid flowing in conduit 21. Y

From extractor 2| the hydrofluoric acid extract is passed through conduit 42 to alkylator 6, carrying With it the extracted organic iiuorine compounds, Which thus lbecome available for the alkylation in alkylator 6 with advantageous recovery of the organic fluorine as hydrogen fluoride.

From extractor 2l the organic fluorine-depleted Vhydrocarbon mixture is passed through conduit 43 to fractionator I9, which generally is a system of fractional-distillation columns. From this system hydroluoric acid dissolved in the hydrocarbon mixture is distilled overhead in company With some isobutane and is passed through conduit 44 to alkylator E. Isobutane is recycled to alkylators 5 and Ii through conduits 45 and 45. No-rmal butane is Withdrawn through outlet 41, or is passed to dehydrogenator 8 by means not shown. A motor fuel of high octane rating is withdrawn as the principal product of the process through outlet 48. A small fraction' of heavy hydrocarbons may be Withdrawn through outlet 49.

It will be understood that the flow-diagram is schematic and that auxiliary equipment, not

11 shown or described, such as pumps, valves, controllers, and the like, may be desirable or even necessary at various points in the process. As such auxiliary equipment are well known, they can be readily supplied by those skilled in the art.

The following data are illustrative of some of many aspects of the invention, without being necessarily limitative.

Two continuous pilot-plant runs were made for the alkylation of isobutane with butene-l under similar alkylation conditions except that in one run the hydrofluoric acid contained 5.0 per cent by weight of water (based on anhydrous HF), whereas in the other run the acid was anhydrous. The data obtained may be summarized as follows:

With Without Run water water Temperature, F 92 88 Contact time, min 1o. 1 11. 1 Isobutane/butene-l (mol) 4. 7:1 4. 7:1 Hydrocarbons/HF (1701.). 1:1 1:1 Organic F in hydrocarbon effluent, wt per cent 0. 0165 0. 0159 Total debutanized alkylate:

Gravity, API 68,1 67. 8 Reid vapor pressure, Ib 2, 30 2. 75 ASTM distillation, F

First drop 178 162 5% evap. 202 196 10 210 203 20.- 214 213 30-- 218 218 40-- 221 223 50-- 223 227 60-. 227 233 70 231 239 80-. 238 253 90.- 252 293 95.- 325 380 Dry poin 392 463 ASTM octane number. 91, 0 85. 3 Light Alkylate:

Cut Point, F 365 365 Yield, vol. per cent of total 97. 2 92. 5 Gravity, API 68, 4 69.0 Reid vapor pressure, lb 1, 75 2. 80 ASTM distillation, F.-

First drop 190 151 206 194 211 204 215 212 218 216 220 220 222 224 224 227 227 229 232 234 242 250 270 302 358 368 92.0 87. 4

It will be noted that the octane number of the i total alkylate was increased by 5.7 units because of the presence of the water in the hydrouoric acid and that the octane number of the light or aviation-range alkylate was increased by 4.6 units. Furthermore, it will be noted that the light alkylate constituted 97.2 per cent of the total alkylate when water was present, whereas it was only 92.5 per cent when Water was absent, indicating that the formation of exceedingly heavy hydrocarbons was advantageously decreased; inasmuch as the yield of total alkylate was approximately the same in both runs, being approximately 200 per cent by weight of the original butene- 1, this fact indicates that an advantageously somewhat higher yield of light alkylate is obtained from butene-l when the present invention is practiced.

It may -be pointed out that in both these runs the mol ratio of isobutane to butene-l in the feed was fairly low, 4.721. There are a number of factors that at present make it 'desirable to conduct commercial alkylation at such a fairly low value for this ratio, even though it Causes the yield and the quality of the alkylate to be somewhat adversely aiiected. When as at present, the need for high-quality alkylate is great, the available alkylation equipment is quite 1limited, and the amount of isobutane is insuicient for al1 needs, it is desirable to conduct the alkylation at afairly low mol ratio of isobutane to olen, in the interest of obtaining as much alkylate as possible from the available isobutane with the available equipment. Also, for a given output of a1- kylate, the concomitant undesirable isomerization of isobutane to normal butane that occurs during alkylation is decreased by decrease in the ratio of isobutaneto olefin, so that the over-all consumption of isobutane is decreased. In line with these considerations, it may be observed that the yield and the quality of the alkylate obtained in the run made without water reflect the innuence of the ratio of isobutane to butene-l, for at a mol ratio twice as large the yield of light alkylate is approximately 98 per cent by volume of the total alkylate and the octane number is approximately 89. But in the run made with water, the yield and the octane number of the alkylate approach closely those that are obtained in hydroluoric acid alkylation of isobutane with butene-Z without water at a mol ratio of isobutane to olefin approximately twice that used in the present run. In other Words, the practice of this invention appears to contribute the unexpected but important advantage of overcoming to a large degree the unfavorable influence attending a low value for the ratio of isobutane to ole- 1in in the feed.

Although the advantages of some aspects of the present invention are obtained when the alkylating olefin is substantially solely butene-l, other advantages are obtained in addition when the detailed procedure indicated by the drawing is followed. This procedure provides a unitary, integrated process for alkylating with both butene-1 and butent-2, each under conditions peculiarly adapted to obtaining an alkylate of optimum yield and quality. This result is obtained with the use of a minimum of equipment and with less expenditure of time, eiort, and materi-l als than is required by a process calling for separate isomerization of butene-l to butene-Z, followed by conventional hydroiiuoric acid alkylation of isobutane, such as that disclosed in the aforementioned copending application, Serial Number 467,873.

Inasmuch as this invention may be practiced other wise than as specifically described or illustrated, and inasmuch as many variations and modifications of it will 'be obvious to those skilled in the art, this invention should not be restricted otherwise than as specied in the appended claims.

I claim:

1. In a process for the alkylation of isobutane with butenes comprising normal butenes in the presence of a concentrated hydroiiuoric acid catalyst, the improvement which comprises maintaining in said hydrofluoric acid catalyst a content of a water in weight per cent of hydrogen fluoride present within a range, the approximate lower limit of which range is determined by 4 times the mol fraction of butane-1 of the total of the butenes plus 2 times the mol fraction of butene-Z of the total of the butenes and the approximate upper limit of which range is determined by 6 times the mol fraction of butene-l of the total of the butenes plus 4 times the mol fraction of butene-Z of the total of the butenes.

2. In a process for the alkylation of isobutane with a mixture of normal butenes in the presence of a concentrated hydrofluoric acid catalyst, the improvement which comprises maintaining in said hydrofluoric acid catalyst a content of Water in Weight per cent of hydrogen fluoride present which is 5 times the mol fraction of butene-l of the total of the butenes plus 3 times the m01 fraction of butene-2 of the total of the butenes.

MARYAN P. MATUSZAK.

REFERENCES CITED The following references are of record in the le of this patent:

Number Number UNITED STATES PATENTS Name Date Grosse et a1. Dec. 30, 1941 Matuszak June 1, 1943 Frey Apr. 27, 1943 Frey June 29, 1943 Linn Feb. 29, 1944 Blount Aug. 22, 1944 FOREIGN PATENTS Country Date Australia Aug. 5, 1943 

